Device for Producing a Non-Thermal Atmospheric Pressure Plasma and Active Space Comprising Such a Device

ABSTRACT

In an embodiment a device includes a first housing in which a piezoelectric transformer is arranged and a second housing in which a control circuit is arranged, the control circuit configured to apply an input voltage to the piezoelectric transformer, wherein the piezoelectric transformer is configured to ionize a process medium, and wherein the device is configured to provide a circulating air operation so that the process medium is guided from the piezoelectric transformer through a catalytic converter and then back to the piezoelectric transformer and generate a non-thermal atmospheric pressure plasma.

This is a continuation application of U.S. application Ser. No.16/494,274 entitled “Device for Producing a Non-Thermal AtmosphericPressure Plasma and Active Space Comprising Such a Device,” which wasfiled on Sep. 13, 2019, which is a national phase filing under section371 of PCT/EP2018/056410, filed Mar. 14, 2018, which claims the priorityof German patent application 102017105430.8, filed Mar. 14, 2017, eachof which is incorporated herein by reference in its entirety.

TECHNICAL FIELD

The present invention relates to a device for producing a non-thermalatmospheric pressure plasma. The present invention further relates to anactive space comprising such a device.

SUMMARY OF THE INVENTION

The non-thermal atmospheric pressure plasma can be produced using apiezoelectric transformer. In particular, the transformer can be aRosen-type transformer.

Embodiments provide an improved device for producing non-thermalatmospheric pressure plasma, which, for example, has a long servicelife. The device should preferably be suitable for use in an activespace, for example, a refuse bin, a garbage can, a sports bag, a closetor a garment bag.

Various embodiments provide a device for producing a non-thermalatmospheric pressure plasma comprising a first housing, in which apiezoelectric transformer is arranged, and a second housing, in which acontrol circuit is arranged, which is designed to apply an input voltageto the piezoelectric transformer. Accordingly, the piezoelectrictransformer and the control circuit can be spatially separated from eachother by the first and the second housing.

The control circuit comprises a time circuit, which applies the inputvoltage to the piezoelectric transformer for a predefined period of timeand which does not apply any input voltage to the piezoelectrictransformer at a predefined pause interval between two periods of time,wherein the application of the input voltage is prevented for theduration of the pause interval. In the pause interval, it thereforecannot be possible to apply an input voltage to the piezoelectrictransformer. As a result, a quantity of ozone which can be produced bythe device can be limited to a level that is not harmful to health.Plasma and ozone generation cannot be possible during the pauseinterval.

The device can be operated in a pulsed mode, in which the transformercan be activated on the basis of the time circuit without taking intoaccount other operating parameters of the transformer and be deactivatedfor the duration of the pause intervals. In any case, the purelytime-based control system can allow the ozone generation rate to belimited to a level that is harmless to health.

This arrangement of the piezoelectric transformer in the first housingand the control circuit in the second housing brings numerousadvantages. If a plasma is generated with the piezoelectric transformer,irritant gases, such as ozone, can form during plasma production. Theseirritant gases are sometimes aggressive and can damage the controlcircuit over time. However, since the control circuit is arranged herein the second housing, damage to the control circuit by the irritantgases can be prevented. This can increase the service life of thedevice. The first housing and the second housing can preferably bedesigned in such a way that a gas exchange between the two housings isminimized. Accordingly, an irritant gas produced in the first housingcannot enter the second housing or can only enter the second housing ina negligible concentration.

In the output region of the piezoelectric transformer, electric fieldswith high field strengths can be created during plasma generation. Thespatial separation of the piezoelectric transformer and the controlcircuit can ensure that the control circuit is not affected by theelectric fields in an undesirable way.

Furthermore, by means of the arrangement of the transformer in the firsthousing and the arrangement of the control circuit in the secondhousing, a user can be better protected from irritant gases. The userwill usually operate the second housing to switch on the control circuitor make changes to the control system. Since the piezoelectrictransformer is arranged separately therefrom in the first housing,irritant gases are only produced in the vicinity of the first housingand hence, not in the immediate vicinity of the user. This can increaseuser safety. This can make it possible to use the device in end productsfor end users who are subject to high safety level requirements.

By dividing it into separate housings, the device can be easy to handle.The device can be designed in a small and compact manner.

For example, the piezoelectric transformer used here can be a componentmarketed by EPCOS under the name CeraPlas™.

The piezoelectric transformer can be designed to produce apiezoelectrically ignited microplasma on an output-side end face of thepiezoelectric transformer. This can be so-called Piezoelectric DirectDischarge Plasma (PDD). The plasma can therefore form directly at thepiezoelectric transformer. Thereby, no additional dielectric barrier isprovided in front of the output-side end face.

Alternatively, a dielectric barrier can be arranged directly in front ofthe output-side end face of the transformer, wherein the barrier can beformed, for example, by an attachment. In this case, the plasma can beproduced similarly to a dielectric barrier discharge (DBD). However, incontrast to a “classic” dielectric barrier discharge, the barrier is notconnected to a high-voltage source by a cable, but is located in closespatial proximity to the piezoelectric transformer so that a highvoltage generated by the transformer can be capacitively coupled into anignition chamber, which is separated from the transformer by thebarrier.

The first housing and the second housing can be separate from eachother. The housings cannot be designed as a single piece. The firsthousing is not arranged inside the second housing and the second housingis not arranged inside the first housing. The housings can be spatiallyseparated from each other. The housings can be arranged side by side,wherein the two housings are either directly connected to each other orarranged at a distance from each other. The first housing and the secondhousing can be designed to provide a spatial separation between thepiezoelectric transformer and the control circuit. The first housing andthe second housing can be designed to ensure that a gas exchange betweenthe two housings only takes place to an insignificant extent.

The control circuit and the piezoelectric transformer can be connectedto each other via a cable. The cable can make it possible to apply analternating voltage output by the control circuit to the externalelectrodes of the piezoelectric transformer as input voltage. Thecontrol circuit can be designed in such a way that it is not influencedby the impedance of the cable. Accordingly, the cable can have a lengthof up to 10 m. The cable can have a length of at least 1 cm. The cablepreferably has a length ranging between 10 cm and 100 cm.

In the first housing there can be arranged a control element, whichmakes it possible to control the plasma generation. Alternatively, thecontrol element can be arranged in the second housing. For example, thecontrol element can be a push-button, a knob, amicrocontroller-controlled system with or without a touchscreen, aremote control or a system that is controlled via USB, WLAN orBluetooth. Furthermore, it can be a control by means of software, suchas an app. The control element can allow a user of the device to controlthe control circuit and to influence and read various parameters duringplasma generation, such as the input voltage, the amount of the processgas that is supplied to the transformer, the concentration of thecomponents of the process gas, the input power and the operating time.

If the control element is arranged on the second housing, it isspatially separated from the piezoelectric transformer located in thefirst housing. Accordingly, safety can be increased for a user whooperates the control element, as he/she does not have to be in theimmediate vicinity of the transformer, which can produce potentiallyharmful irritant gases.

The first housing can comprise a nozzle, which is arranged in front ofan end face of the piezoelectric transformer and is designed to form aplasma beam generated by the piezoelectric transformer.

Furthermore, the first housing can have a dielectric barrier, which isarranged immediately in front of the piezoelectric transformer. Thedielectric barrier can separate the piezoelectric transformer from anignition chamber, in which the process medium is arranged. A highvoltage generated by the piezoelectric transformer can be capacitivelycoupled in the ignition chamber via the dielectric barrier and trigger aplasma ignition there. Such an embodiment is particularly advantageousin the case of liquid process media or in the case of biological tissueas a process medium. In this case, the piezoelectric transformer doesnot come into direct contact with the process medium. This directcontact would mechanically dampen the transformer and it could no longerbe used to generate plasma. Since direct contact is prevented by thebarrier, mechanical damping can be prevented from the beginning. Thearrangement of a dielectric barrier in front of the transformer is alsouseful for other process media that are very aggressive and could damagethe piezoelectric transformer.

The device can comprise a third housing, which also comprises apiezoelectric transformer. The first housing can be replaceable and bereplaced by the third housing. In this case, the control circuit afterthe replacement of the first housing by the second housing can bedesigned to apply the input voltage to the piezoelectric transformerarranged in the third housing.

Accordingly, the piezoelectric transformer can be replaced together withthe first housing. The piezoelectric transformer is the component of thedevice that is most exposed to signs of wear. By means of theembodiment, in which the first housing is replaceable, it is madepossible to replace only the transformer and to continue to use thecontrol circuit and other elements, which are arranged in the secondhousing.

The piezoelectric transformer can be replaced as a module together withthe first housing. The first housing and the second housing can beconnected to each other via a detachable connection, for example, a plugconnection, a USB connection or a bayonet connection. Such a connectionis easy for a user to detach so that a replacement of the module withthe first housing and the piezoelectric transformer can be made in asimple manner. On the other hand, replacing the piezoelectrictransformer without simultaneously exchanging the first housing would beconsiderably more complex since, in this case, the attachment of thetransformer to the housing would have to be detached.

The third housing can comprise a nozzle. The first housing can alsocomprise a nozzle. The nozzles can be designed to shape the plasma beamin different ways or to attach a dielectric barrier in front of thetransformer. Accordingly, the first housing and the third housing can beinterchanged among each other to change a form of the plasma beam in adesired way. A separate replacement of only the nozzle without replacingthe entire first housing, on the other hand, would be considerably morecomplex since, in this case, the attachment of the nozzle to the housingwould have to be detached and the new nozzle would have to be attachedto the housing again.

In an alternative exemplary embodiment, the nozzle can be replacedseparately. A nozzle attached to the first housing or to the thirdhousing can in this case be replaceable. Preferably, the nozzle is inthis case attached to the respective housing by means of an attachmentthat can be easily detached.

For example, the nozzle can be attached to the respective housing bymeans of a bayonet connection. The nozzle can also be attached to therespective housing by means of a snap-on connection or a screwconnection.

The first housing can be designed to eradicate irritant gases producedduring plasma production. For this purpose, the first housing cancomprise a coating. The coating can, for example, comprise manganesedioxide, iron oxide, other metal oxides, bare metal surfaces or surfacescoated with metal catalysts, or lacquers. In addition, or as analternative, the housing can comprise a filter to eradicate the irritantgases. For example, the filter can be an activated-carbon filter. Inaddition, or as an alternative, the housing can be designed in such away that a closed gas guidance system results, in which irritant gasesare prevented from flowing out of the housing. In addition, or as analternative, the housing can comprise a suction device. This can bedesigned to suck up irritant gases immediately after their production.At most only partial gas recirculation into the first housing can alsobe provided, wherein the first housing for the eradication of theirritant gas can be appropriately coated.

The device can comprise a control mechanism, which makes it possible toadjust an amount of a process medium, which is supplied to thepiezoelectric transformer. In addition, or as an alternative, thecontrol mechanism also can make it possible to adjust a composition ofthe process medium.

The device can comprise an attachment, which is attached to the firsthousing and which forms a dielectric barrier immediately in front of anoutput-side end face of the piezoelectric transformer, so that thedevice is designed to ignite a plasma by means of a dielectric barrierdischarge on a side of the dielectric barrier facing away from thetransformer.

A plurality of piezoelectric transformers can be arranged in the firsthousing. The control circuit arranged in the second housing can beconnected to each of the transformers and designed to apply an inputvoltage to each of the transformers.

The control circuit can comprise a time circuit, which applies the inputvoltage to the piezoelectric transformer for a predefined period of timeand which does not apply any input voltage to the piezoelectrictransformer at a predefined pause interval between two periods of time.For example, an input voltage can be applied to the transformer for aperiod of 15 seconds and no input voltage can be applied during a pauseinterval lasting 2 hours. In this way, energy consumption of the devicecan be minimized and the irritant gas concentration can be limited.

The first housing and the second housing can be formed by two chambersof an injection-molded part. The first housing and the second housingcan be separated from each other in a watertight manner. The firsthousing and the second housing can be separated from each other in agastight manner.

In the second housing there can be arranged energy supply means of thedevice. The energy supply means can be, for example, a battery,rechargeable batteries that can be charged in one embodiment by means ofcontactless inductive charging, or a transformer designed to convert amains voltage into an operating voltage of the device. Since the energysupply means are arranged in the second housing, they can be reused whenthe first housing is replaced.

The device can be a portable handheld device.

In the second housing there can be arranged process-gas-supply means,wherein the device comprises a hose, which is designed to guide aprocess gas from the process-gas-supply means out of the second housingto the piezoelectric transformer arranged in the first housing. The hosecan be integrated into a cable that connects the first housing to thesecond housing. If the first housing is replaced, the process-gas-supplymeans can thus be reused. The process-gas-supply means can be, forexample, a fan, a compressor or a connection for various compressed gastanks, using a gas mixer if applicable. Furthermore, theprocess-gas-supply means can comprise a pressure reducer, a mass flowcontroller, a gas humidifier, a gas dryer, an atomizer and a nebulizer.Alternatively, the means for process gas management can also beintegrated into the first housing.

The medium in which the plasma is ignited can be referred to as themedium medium. For example, the process medium can be ambient air of thepiezoelectric transformer. The process medium can also be any materialpresent that is gaseous at the operating temperature and the operatingpressure, all conceivable material mixtures that are gaseous at theoperating temperature and the operating pressure, an aerosol, whichcomprises liquid and/or solid particles floating in gas, a liquid, orbiological tissue. The operating pressure and the operating temperatureindicate the pressure or the temperature at which the device forproducing the non-thermal atmospheric pressure plasma is commonly used.In particular, the operating pressure can be an atmospheric pressure.The operating pressure can be between 0.2 bar and 1.5 bar, preferablybetween 0.8 bar and 1.2 bar. The operating temperature can be, inparticular, a room temperature. The operating temperature can be in arange between −50° C. and +155° C., preferably between 0° C. and 45° C.

If the process medium is a gaseous substance, it can be, for example, apure gas, for example, pure He, pure Ar, pure N₂, pure O₂, pure CO₂,pure H₂ or pure Cl₂. Furthermore, the process medium H₂O can be in thesupercritical area. The process medium can have supercritical, meaning,non-condensable pure substances at the operating temperature andoperating pressure.

The process medium can comprise one or a mixture of a plurality of theaforementioned pure gases or the following gases: air, inert gas andforming gas. The process medium is selected in such a way that the gasstate is maintained at the operating temperature and operating pressure.

The process medium can have a liquid aerosol in a gas or a gas mixture.For example, it can be air above the dew point, saturated steam or agasoline/diesel air mixture. The process medium can have a solid aerosolin a gas or a gas mixture. This can be, for example, soot in exhaust gasor particulate matter in air. For medical and technical applications,particularly good results can be achieved when using aerosols as aprocess medium. The aerosol can, in particular, be water droplets inair. It can also be droplets of H₂O₂ or formaldehyde. By treating thewater droplets with plasma, OH radicals can be produced. In addition,water droplets can be used to bind the resulting irritant gases, such asozone or nitric oxide, and thus to reduce the environmental load withthese gases in order to increase the application safety. This irritantgas binding can additionally cause an increase in activity by irritantgas in particular for sterilization, for example, by ozone dissolved inwater droplets. The device could also be used in exhaust gas streams forparticle separation. The device could also be used in steam circuits orsanitary rooms, as well as their ventilation circuits, wherein alsoaerosols can form the process medium.

The device can comprise a suction spout, which is designed to suck up anirritant gas produced by the piezoelectric transformer, wherein theirritant gas is eradicated in the suction spout.

The device can comprise a sensor for determining a filling level,temperature or humidity. The sensor measures the corresponding parameterinside or around the active space.

The device can include circuit components of a remote control. Thecircuit components are used to control a control system. The remotecontrol can allow by way of a program or an app for a computer, such asa PC or a mobile communication device, to read out the state of thedevice or to control the device.

The device can comprise circuit elements for recording parameters suchas the operating time, errors that have occurred, status information orother operating parameters. By means of a memory, it is possible toobtain values in a log file.

The device can comprise one or a plurality of indicators for the opticalor acoustic signaling of one or a plurality of operating parameters.

The device can be provided and suitable for enabling, accelerating orcatalyzing chemical reactions.

The device can be provided and suitable for activating or sterilizingsurfaces.

The device can be provided and suitable for treating or cleaning livingand biological tissue. In particular, it can be used for the treatmentor purification of open or closed or poorly healing wounds inside or onthe exterior of a living human or animal body. In particular, theapplication to skin wounds is preferred, wherein these wounds can be, inparticular, poorly healing, poorly supplied with blood or germ-infectedwounds.

In the first housing there can be arranged a fan and a catalyticconverter, wherein the fan is designed to ensure a circulating airoperation where a process medium ionized by the piezoelectrictransformer in the first housing is guided within a circuit, and therebyis guided through the catalytic converter before the process medium issupplied back to the piezoelectric transformer.

The first housing can comprise a heat exchanger, which is arranged anddesigned to dissipate heat from the inside of the first housing to anenvironment.

The input region of the piezoelectric transformer can rest on a firstsupport element, wherein the device comprises at least one projection,which is at a distance from the piezoelectric transformer if thetransformer is at a state of rest, and which forms an end-stop againsttransverse movements of the piezoelectric transformer. The projectioncan be arranged at half the length of the transformer. The projectioncan be at a distance from the piezoelectric transformer when thetransformer is at a state of rest.

The spacing of the projection is chosen in such a way that thepiezoelectric transformer does not hit the projection at its state ofrest, even with normal manufacturing tolerances and thermal expansions.The projection is arranged in such a way that it limits movements of thetransformer due to deformations of the transformer during operationand/or due to impacts on the device and forms an end-stop for thetransformer in the case of such movements.

The device can comprise a second projection, which is at a distance fromthe piezoelectric transformer when the transformer is at a state ofrest, and which forms an end-stop against transverse movements of thepiezoelectric transformer, wherein the second projection is arranged atan input-side end of the transformer. The spacing of the secondprojection is chosen in such a way that the piezoelectric transformerdoes not hit the second projection at its state of rest, even withnormal manufacturing tolerances and thermal expansions. The secondprojection is arranged in such a way that it limits movements of thetransformer due to deformations of the transformer during operationand/or due to impacts on the device and forms an end-stop for thetransformer at such movements.

According to a further aspect, a device for producing a non-thermalatmospheric pressure plasma is proposed, comprising a first housing, inwhich a piezoelectric transformer is arranged, and a second housing, inwhich a control circuit is arranged, which is designed to apply an inputvoltage to the piezoelectric transformer, wherein the first housing foreradicating the irritant gases comprises a coating. The coating can bemanganese dioxide, iron oxide, other metal oxides, bare metal surfacesor a surface coated with metal catalysts, or lacquers.

According to a further aspect, a device for producing a non-thermalatmospheric pressure plasma is proposed, comprising a first housing, inwhich a piezoelectric transformer is arranged, and a second housing, inwhich a control circuit is arranged, which is designed to apply an inputvoltage to the piezoelectric transformer, and wherein in the firsthousing there is arranged at least one control element, which makes itpossible to control the plasma generation.

According to a further aspect, the present invention relates to anactive space comprising the device described above and a gas volume. Thegas volume can be airtight or not be airtight. The device can be used totreat gas present in the gas volume with plasma and/or ozone, forexample, to avoid or reduce an odor.

The active space can also be called the effective volume. The activespace can be a spatially limited area, the content of which is treatedwith the plasma generated by the device. The active space can therebybe, for example, a reservoir. The active space does not necessarily haveto comprise a closed volume. Rather, a continuous gas exchange can occurin an active space with a gas volume that is not airtight, so that thegas in the active space is continuously renewed or replaced.

A refuse bin, a garbage can and a plastic bag can, for example, form anactive space with an airtight gas volume. A sports bag or a cotton bagcan form an active space with a gas volume that is not airtight.Furthermore, the use in cabinets, for example, closets, is conceivableas an active space. It can also be used in garment bags or shoe bags.

If the device is used in an active space with a gas volume that is notairtight, precautions can preferably be taken to limit an irritant gasconcentration and quickly break it down. In particular, the firsthousing that has the transformer, as already discussed above, can bedesigned to eradicate irritant gases produced during the plasmaproduction. For this purpose, the first housing can comprise a coating,for example, manganese dioxide or iron oxide. As an alternative or inaddition, the housing can comprise a filter to eradicate the irritantgases. As an alternative or in addition, the housing can be designed insuch a way that a closed gas guidance system results, in which irritantgases are prevented from flowing out of the housing. As an alternativeor in addition, the housing can comprise a suction device that isdesigned to suck up irritant gases directly after they are produced.Alternatively, the housing can have a partial irritant gas guide or(gas) return, wherein the housing for the eradication of the irritantgases can be appropriately coated. Furthermore, the device can have anacoustic and/or optical warning device designed to alert a user in theevent of a questionable irritant gas concentration. As an alternative orin addition, the device can be designed to automatically switch off atan irritant gas concentration above a threshold value. The device canalso be designed to switch on again when the irritant gas concentrationhas fallen below the threshold value.

The device can be compactly integrated into the active space andcomprise a perforation for ozone to flow out. The device can beremovable from the active space. Alternatively, only the first housingcan also be installed within the active space. The second housing can bearranged outside the active space.

The active space can, for example, have a cover, wherein the device orat least the first housing is arranged on the cover. A plasma outletopening of the device can point away from the cover. The plasma outletopening points in the direction of an active space or an effectivevolume. The device can alternatively be installed at another position inthe active space, for example, in a side wall.

The device can comprise an outlet opening, from which plasma generatedby the transformer can flow out. The device can be arranged in such away that the outlet opening is arranged inside the active space. Thedevice can also have an inlet opening, through which a gaseous processmedium can penetrate into the first housing. The device can be arrangedin such a way that the inlet opening is arranged outside the activespace. Furthermore, the device can have a carbon filter, which isarranged between the inlet opening and the outlet opening and whichseparates the interior of the active space from the surroundings of theactive space. In particular, the carbon filter can prevent an irritantgas produced inside the active space from entering the surroundings ofthe active space.

Alternatively or in addition to the carbon filter, the device, inparticular to prevent an outlet of the irritant gas produced inside theactive space into the surroundings of the active space, can be providedwith a coating degrading irritant gas.

The active space can comprise a sensor, which is designed to detect anopening or closing of the cover, wherein the device is designed toproduce a plasma after closing the cover. For example, the sensor can bean inclination sensor, an accelerometer, or a light sensor.

In the following, favorable aspects are described. To facilitatereferencing, the aspects are numbered. Features of the aspects arerelevant not only in combination with the specific aspect to which theyrelate, but also in a separate way.

Aspect 1: A device for producing a non-thermal atmospheric pressureplasma, comprising a first housing, in which a piezoelectric transformeris arranged, and a second housing, in which a control circuit isarranged, which is designed to apply an input voltage to thepiezoelectric transformer.

Aspect 2: The device according to the previous aspect, wherein thepiezoelectric transformer is designed to produce piezoelectricallyignited microplasma on an output-side end face of the piezoelectrictransformer.

Aspect 3: The device according to any one of the previous aspects,wherein the first housing and the second housing are separate from eachother.

Aspect 4: The device according to any one of the previous aspects,wherein the control circuit and the piezoelectric transformer areconnected to each other via a cable.

Aspect 5: The device according to the previous aspect, wherein the cablehas a length of at least 1 cm.

Aspect 6: The device according to any one of the previous aspects,wherein in the first housing there is arranged at least one controlelement, which makes it possible to control the plasma generation orwherein in the second housing there is arranged at least one controlelement, which makes it possible to control the plasma generation.

Aspect 7: The device according to any one of the previous aspects,wherein the first housing comprises a nozzle, which is arranged in frontof an end face of the piezoelectric transformer and which is designed toform a plasma beam generated by the piezoelectric transformer.

Aspect 8: The device according to any one of the previous aspects,wherein the device comprises a third housing, which has a piezoelectrictransformer, wherein the first housing is replaceable and can bereplaced by the third housing.

Aspect 9: The device according to any one of the previous aspects,wherein the first housing is designed to eradicate irritant gasesproduced during the plasma production.

Aspect 10: The device according to the previous aspect, wherein thefirst housing comprises a coating and/or a filter and/or a closed gasguidance system and/or a suction device to eradicate the irritant gases.

Aspect 11: The device according to any one of the previous aspects,wherein the device comprises a control mechanism, which makes itpossible to adjust the amount and/or a composition of a process medium,which is supplied to the piezoelectric transformer.

Aspect 12: The device according to any one of the previous aspects,wherein the device comprises an attachment, which is attached to thefirst housing and which forms a dielectric barrier immediately in frontof an output-side end face of the piezoelectric transformer, so that thedevice is designed to ignite a plasma by means of a dielectric barrierdischarge on a side of the dielectric barrier facing away from thetransformer.

Aspect 13: The device according to any one of the previous aspects,wherein a plurality of piezoelectric transformers are arranged in thefirst housing.

Aspect 14: The device according to any one of the previous aspects,wherein the control circuit comprises a time circuit, which applies theinput voltage to the piezoelectric transformer for a predefined periodof time and which does not apply any input voltage to the piezoelectrictransformer at a predefined pause interval between two periods of time.

Aspect 15: The device according to any one of the previous aspects,wherein the first housing and the second housing are formed by twochambers of an injection-molded part.

Aspect 16: The device according to any one of the previous aspects,wherein the first housing and the second housing are separated from eachother in a watertight manner.

Aspect 17: The device according to any one of the previous aspects,wherein the first housing and the second housing are separated from eachother in a gastight manner.

Aspect 18: The device according to any one of the previous aspects,wherein an energy supply of the device is arranged in the secondhousing.

Aspect 19: The device according to any one of the previous aspects,wherein the device is a portable handheld device.

Aspect 20: The device according to any one of the previous aspects,wherein process-gas-supply means are arranged in the second housing,wherein the device comprises a hose, which is designed to guide aprocess gas from the process-gas-supply means out of the second housingto the piezoelectric transformer arranged in the first housing.

Aspect 21: The device according to any one of the previous aspects,wherein the device comprises a suction spout, which is designed to suckup an irritant gas produced by the piezoelectric transformer, whereinthe irritant gas is eradicated in the suction spout.

Aspect 22: The device according to any one of the previous aspects,furthermore comprising a sensor for determining a filling level,temperature or humidity inside or in the surroundings of the activespace.

Aspect 23: The device according to any one of the previous aspects,furthermore comprising circuit components of a remote control forcontrolling a control system.

Aspect 24: The device according to any one of the previous aspects,furthermore comprising circuit elements for recording the operatingtime, errors, status information, operating parameters.

Aspect 25: The device according to any one of the previous aspects,furthermore comprising one or a plurality of indicators for the opticalor acoustic signaling of one or a plurality of operating parameters.

Aspect 26: The device according to any one of the previous aspects, forenabling, accelerating or catalyzing chemical reactions.

Aspect 27: The device according to any one of the previous aspects,which is provided to activate or to sterilize surfaces.

Aspect 28: The device according to any one of the previous aspects,which is provided to clean or to treat wounds of a human or animal body.

Aspect 29: An active space comprising a device according to any one ofthe previous aspects and a gas volume that is airtight or a gas volumethat is not airtight.

Aspect 30: The active space according to the previous aspect, whereinthe active space comprises a cover and wherein the device is arranged onthe cover, wherein a plasma outlet opening of the device points awayfrom the cover.

Aspect 31: The active space according to the previous aspect, whereinthe active space comprises a sensor, which is designed to detect anopening and closing of the cover, wherein the device is designed toproduce plasma after closing the cover.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the present invention is described in more detailbased on the enclosed figures.

FIG. 1 shows a piezoelectric transformer in a perspective view;

FIG. 2 shows a device for plasma generation according to a firstexemplary embodiment;

FIG. 3 shows a piezoelectric transformer, which is arranged in amounting;

FIG. 4 shows a device for plasma generation according to a secondexemplary embodiment;

FIGS. 5 to 7 show a device for plasma generation according to a thirdexemplary embodiment;

FIG. 8 shows a first part of a device for plasma generation according toa variation of the third exemplary embodiment;

FIG. 9 shows a first housing according to a further exemplaryembodiment;

FIG. 10 shows a first housing according to a further exemplaryembodiment;

FIGS. 11, 12 and 13 show a mounting for a piezoelectric transformer; and

FIG. 14 shows an application of an input voltage to a piezoelectrictransformer in intervals; the transformer is activated in a firstinterval and deactivated in a pause interval.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

FIG. 1 shows a piezoelectric transformer 1 in a perspective view. Inparticular, the piezoelectric transformer 1 can be used in a device forproducing non-thermal atmospheric pressure plasma.

A piezoelectric transformer 1 is a design of a resonance transformer,which is based on piezoelectricity and, in contrast to the conventionalmagnetic transformers, represents an electromechanical system. Forexample, the piezoelectric transformer 1 is a Rosen-type transformer.

The piezoelectric transformer 1 has an input region 2 and an outputregion 3, wherein the output region 3 connects in a longitudinaldirection z to the input region 2. In the input region 2, thepiezoelectric transformer 1 comprises electrodes 4, to which analternating voltage can be applied. The electrodes 4 extend in thelongitudinal direction z of the piezoelectric transformer 1. Theelectrodes 4 are stacked alternately with a piezoelectric material 5 ina stacking direction x, which is perpendicular to the longitudinaldirection z. The piezoelectric material 5 is polarized in the stackingdirection x.

The electrodes 4 are arranged inside the piezoelectric transformer 1 andare also referred to as internal electrodes. The piezoelectrictransformer 1 comprises a first side surface 6 and a second side surface7, which is opposite the first side surface 6. On the first side surface6 a first external electrode 8 is arranged. On the second side surface 7a second external electrode (not shown) is arranged. The internalelectrodes 4 are in the stacking direction x alternately contactedeither with the first external electrode 8 or the second externalelectrode electrically.

The input region 2 can be controlled with a low alternating voltage,which is applied between the electrodes 4. Due to the piezoelectriceffect, the alternating voltage applied on the input side is initiallyconverted into a mechanical oscillation. The frequency of the mechanicaloscillation depends essentially on the geometry, the mechanicalstructure and the material of the piezoelectric transformer 1.

The output region 3 comprises piezoelectric material 9 and is free ofinternal electrodes. The piezoelectric material 9 in the output region 3is polarized in the longitudinal direction x. The piezoelectric material9 of the output region 3 can be the same material as the piezoelectricmaterial 5 of the input region 2, wherein the piezoelectric materials 5and 9 can differ in their polarization direction. In the output region3, the piezoelectric material 9 is formed into a single monolithiclayer, which is completely polarized in the longitudinal direction z.The piezoelectric material 9 in the output region 3 has only one singlepolarization direction.

If an alternating voltage is applied to the electrodes 4 in the inputregion 2, a mechanical wave which generates an output voltage in theoutput region 3 by means of the piezoelectric effect is formed withinthe piezoelectric material 5, 9. The output region 3 comprises anoutput-side end face 10. In the output region 3, thus, an electricalvoltage is generated between the end face 10 and the end of theelectrodes 4 of the input region 2. A high voltage is generated at theoutput-side end face 10. This also creates a high potential differencebetween the output-side end face and surroundings of the piezoelectrictransformer, sufficient to generate a strong electric field that ionizesa process medium. Furthermore, the generation of radicals, excitedmolecules or atoms in the plasma is possible.

In this way, the piezoelectric transformer 1 generates high electricfields, which are able to ionize gases or liquids by electricalexcitation. Thereby, atoms or molecules of the respective gas or therespective liquid are ionized and form a plasma. An ionization alwaysoccurs if the electric field strength on the surface of thepiezoelectric transformer 1 exceeds the ignition field strength of theplasma. The field strength that is required for the ionization of theatoms or molecules or for the generation of radicals, excited moleculesor atoms is referred to as the ignition field strength of a plasma.

FIG. 2 shows a device for plasma generation, which comprises thepiezoelectric transformer 1 shown in FIG. 1. The device comprises afirst housing 11, in which the piezoelectric transformer 1 is arranged.Furthermore, a mounting 12 which attaches the piezoelectric transformer1 is arranged in the housing 11. The mounting 12 will be explained ingreater detail below in connection with FIG. 3.

The first housing 1 also has a plasma outlet channel 13. The plasmaoutlet channel 13 is arranged in front of the output-side end face 10 ofthe piezoelectric transformer 1. If a process medium is ionized by thepiezoelectric transformer 1 or if radicals, excited molecules or atomsare generated by the piezoelectric transformer 1, a plasma generated inthis way is guided to a desired usage location via the plasma outletchannel 13.

The plasma outlet channel 13 is an optional embodiment of the device.Alternatively, the first housing 11 can have a simple opening from whichthe plasma generated by the piezoelectric transformer 1 can flow out.Alternatively, the housing 11 can comprise a nozzle designed to focus orto fan a plasma beam or which has a dielectric barrier.

The first housing 11 can furthermore comprise a switch for power and/orgas flow control, which makes it possible to adjust which amount of aprocess medium is supplied to the piezoelectric transformer 1. The firsthousing 11 can have a feedback mechanism, which can transmit informationabout the currently generated plasma to a control circuit 14, whereinthe control circuit 14 can also be designed to adapt the control systemof the piezoelectric transformer 1 by taking this information intoaccount.

In the first housing 11 there can be arranged a fan 108 and a catalyticconverter 109, wherein the fan 108 is designed to ensure a circulatingair operation where a process medium ionized by the piezoelectrictransformer 1 in the first housing 11 is guided within a circuit, andthereby is guided through the catalytic converter 109 before the processmedium is supplied back to the piezoelectric transformer 1.

The first housing 11 can comprise a heat exchanger 110, which isarranged and designed to dissipate heat from the inside of the firsthousing 11 to an environment.

The device furthermore comprises a second housing 15. Further elementsof the device are arranged in the second housing 15. In particular, acontrol circuit 14 for the piezoelectric transformer 1 is arranged inthe second housing 15. Furthermore an energy supply 16 of the device isarranged in the second housing 15.

The control circuit 14 is designed to apply an input voltage to thepiezoelectric transformer 1. The control circuit 14 is connected to thepiezoelectric transformer 1 via a cable 17. Due to the design of thecontrol circuit 14, in principle no significant restrictions have to beobserved with regard to the cable length. Furthermore, the controlcircuit 14 does not have to be cooled by a separate cooling device or afan. However, a cooling device can be alternatively provided in order toachieve higher output power in any case.

The cable 17, which connects the control circuit 14 to the piezoelectrictransformer 1, can be connected to the first housing 11 either firmly orby a detachable connection, for example, a plug-in connection. If thecable 17 is connected to the first housing 11 using a detachableconnection, the first housing 11 can be completely removed from thesecond housing 15 when the connection is disconnected, and be replaced,for example, by another housing. The cable 17 can furthermore also beconnected to the second housing 15 either firmly or by a detachableconnection, for example, a plug-in connection.

An additional line, through which information for a feedback mechanismis transmitted from the first housing 11 to the second housing 15, canalso be integrated into the cable 17. This embodiment will be explainedin more detail later on.

As an alternative or in addition, a control element, for example, aswitch, can be arranged on the cable 17, which makes it possible toregulate a gas flow and thus adjust what amount of a gaseous processmedium is supplied to the piezoelectric transformer 1.

As an alternative or in addition, a hose, through which a process mediumis transported out of the second housing 15 into the first housing 11and, in this way, is supplied to the piezoelectric transformer 1, can beintegrated into the cable 17.

The energy supply 16 according to the exemplary embodiment shown in FIG.2 comprises batteries. The power supply 16 can also be rechargeablebatteries. These can optionally be charged by an inductive chargingmethod. Alternatively, the power supply 16 can also be a transformer,which is designed to be connected to a power grid and to transform themains voltage of the power network to an operating voltage of thedevice.

The first and the second housing 11, 15 are spatially separated fromeach other. By the spatial separation of the first and the secondhousing 11, 15, it can be ensured that a gas exchange between the twohousings 11, 15 is minimized. Accordingly, a gas produced in the firsthousing 11 cannot penetrate or at least can penetrate only in anegligibly low concentration into the second housing 15. In this way,the control circuit 14, arranged in the second housing 15, is protectedfrom irritant gases which are produced during the plasma generation inthe first housing 11. Since the control circuit 14 does not come intodirect contact with possibly aggressive irritant gases, these have nonegative influence on the service life of the device. Accordingly, thespatial separation of the two housings 11, 15 allows for a long servicelife of the device.

Furthermore, the spatial separation of the piezoelectric transformer 1and the control circuit 14 and the associated minimization of the gasexchange between the two housings allows the device to integrate alsointo a consumer product. A consumer product is a product that is used byan end customer, for example, for private use. In doing so, specialsafety requirements must be met, according to which a user of the devicemust be protected from potentially harmful irritant gases. It would bepossible, for example, to arrange the second housing 15 with the controlcircuit 14 and with control elements in an area accessible to the enduser and to arrange the first housing 11, which comprises thepiezoelectric transformer 1 and in which potentially harmful irritantgases can form, in an area that is not directly accessible to the enduser. Accordingly, the end user can be protected from the irritant gasesby the spatial separation of the piezoelectric transformer 1 and thecontrol circuit 14.

Since the control circuit 14 makes it possible to dispense with separatecooling, overall the design of a small and light handheld device inwhich the device is integrated is made possible.

In the output region 3 of the piezoelectric transformer 1, electricfields with high field strengths are created during the plasmageneration. Due to the spatial separation of the piezoelectrictransformer 1 and the control circuit 14 in two separate housings 11, 15it can be ensured that the control circuit 14 cannot be disturbed by theelectric fields.

Further elements of the device can also be integrated in the secondhousing 15. For example, a time circuit 101, control elements 102 and acontrol mechanism 103, can be accommodated in the second housing 15. Thecontrol elements 102 can make it possible to give commands to thecontrol circuit 14 and thus to control the plasma generation by thepiezoelectric transformer 1. The control elements 102 can bepush-buttons, knobs, microcontroller-controlled systems with atouchscreen, microcontroller-controlled systems without a touchscreen, aremote control or systems that can be connected to the control circuitvia USB, WLAN or Bluetooth and can transmit control commands to it. Asan alternative or in addition, the control circuit can be operated bymeans of an app or another software. The control elements 102 can alsobe arranged on the cable 17, which connects the first and the secondhousing 11, 15 to each other.

A gas supply, which is designed to guide a gaseous process medium to thepiezoelectric transformer 1, can also be integrated in the secondhousing 15. A hose, through which the gaseous process medium isintroduced into the first housing 11, can also be integrated in thecable 17, which connects the first housing 11 to the second housing 15.

The gas supply can, for example, comprise a fan. The gas supply cancomprise a compressor. The gas supply can have connections to whichvarious compressed gas tanks can be connected. For the mixing ofdifferent gases, the gas supply can also comprise a gas mixer. The gassupply can have a pressure reducer and/or mass flow controller (MFC),which makes it possible to control the amount of the process medium.Furthermore, the gas supply can comprise a gas humidifier or a gas dryeror a nebulizer or an atomizer. Furthermore, it is conceivable to connectthe gas control system to a stationary gas supply via appropriatecouplings and thereby to provide the supply. The stationary gas supplycan be, for example, a compressed air source or gas pressure lines thatprovide, for example, N₂, O₂ or Ar.

The control circuit 14 can be designed to regulate a power and/or gasflow concentration. The control circuit 14 can vary the input voltageapplied to the piezoelectric transformer 1 and/or the process medium,which is supplied to the piezoelectric transformer 1. With regard to theprocess medium, variations of the amount of the supplied process mediumas well as of the composition of the supplied process medium arepossible. For example, the device can comprise a plurality of gascartridges, in which different gases are arranged. The process mediumcan result from a mixture of these gases. By varying the mixing ratio ofthe gases, the properties of the generated plasma can be changed.

The device can have a sensor 104 that detects, for example, a quantityof ozone generated by the piezoelectric transformer 1. The controlcircuit 14 can be designed to vary and/or read out at least one of thefollowing parameters, taking into account the values measured by thesensor 104: the input voltage, the amount of the process medium suppliedto the transformer 1, the composition of the process medium, the inputpower and the operating time.

As an alternative or in addition, the device can be designed to detectwhether a load is arranged in the immediate vicinity of the transformer1. The control circuit 14 can be designed to vary at least one of thefollowing parameters when detecting a load: the input voltage, theamount of the process medium supplied to the transformer, thecomposition of the process medium, the input power and the operatingtime.

The second housing 15 can also comprise a status indicator 107. Forexample, the status indicator 107 can comprise a light-emitting diode.Different colors or different flashing patterns of the light-emittingdiode can communicate information about the operating state or thebattery status of the device. The status display can enable a conditionand/or performance monitoring of the device.

The device can include circuit components of a remote control 105 and acircuit element 106.

The device can also comprise an optical and/or acoustic irritant gaswarning system which warns a user, provided that a predetermined limitvalue for an irritant gas concentration is exceeded in the immediatevicinity of the device.

In an exemplary embodiment (not shown), a plurality of piezoelectrictransformers 1 can be arranged in the first housing 11. The controlcircuit 14 can be designed to apply an input voltage to each of thetransformers 1. The piezoelectric transformers 1 can be operatedparallel to each other. In this way, the amount of a generated plasmacan be increased.

FIG. 3 shows the piezoelectric transformer 1, which is fixed in themounting 12. The mounting 12 has support elements 18, which are arrangedin the longitudinal direction z at a length of one quarter and of threequarters of the total length of the piezoelectric transformer 1 and lieon this in a line-shaped manner. Furthermore, the mounting 12 comprisestwo contact elements 19, which are electrically connected to theexternal electrodes of the piezoelectric transformer 1. The contactelements 19 are, for example, wires or sheets, for example, of copper,Invar, copper/Invar copper (CIC) or stainless steel. The contactelements 19 can be attached to the piezoelectric transformer 1 and canform a positive-locking connection with the mounting 12. In this way, amovement of the transformer 1 in the longitudinal direction z relativeto the mounting 12 can be prevented.

As an alternative to the fastening shown here in the mounting 12, thepiezoelectric transformer 1 can also be arranged together with a fan 108and/or a process-gas supply in a module. Such a module can be arrangedin the first housing 11.

FIG. 4 shows a second exemplary embodiment of the device, wherein thefirst housing 11 and the second housing 15 are arranged directly next toeach other. The two housings are separated from each other by a commonpartition wall 20. The partition wall 20 ensures a spatial separation ofthe transformer 1 arranged in the first housing 11 from the elementsarranged in the second housing 15, in particular the control circuit 14and the energy supply 16.

The first housing 11 also has here a first opening 21, through whichambient air as process medium can be supplied to the piezoelectrictransformer 1. The first opening 21 is a slit-shaped grate. The firsthousing 11 furthermore comprises a second opening 22, through which aplasma generated by the piezoelectric transformer 1 can flow out fromthe first housing 11. The second opening 22 is also a slit-shaped grate.The first opening 21 and the second opening 22 can each be arrangedeither on a top side or a bottom side of the first housing 11. Thesecond opening 22 is arranged at the end of the plasma outlet channel13.

Otherwise, the device shown in FIG. 4 corresponds substantially to thedevice shown in FIG. 2.

Between the first opening 21 of the first housing 11 and thepiezoelectric transformer 1 there can also be arranged anactivated-carbon filter (not shown). The activated-carbon filter absorbsozone and breaks down the ozone quickly and effectively. The firstopening 21 forms an inflow opening through which the gaseous processmedium flows toward the piezoelectric transformer 1. However, if the gasflow within the first housing 11 is reversed, the activated-carbonfilter can prevent ozone from leaking from the first opening 21.Accordingly, the activated-carbon filter increases the safety of theuser in the event of any device faults.

The device can also be designed to prevent the leakage of potentiallyharmful irritant gas from the second opening 22. For this purpose, thedevice can be provided with a coating, for example, made of manganesedioxide or iron oxide, which breaks down ozone. The coating can beapplied, for example, on the inner side of the plasma outlet channel 13.Alternatively, the flow-out of ozone can also be prevented by a filtersystem, which is arranged at the output-side end face 10 of thepiezoelectric transformer 1. Alternatively, since process medium canalso be guided in a closed circuit to prevent the ozone from flowingout. Alternatively, it can also be possible that the device is designedin such a way that a flow of the process medium can be reversed in orderto suck out the irritant gas in a suction operation.

FIGS. 5, 6 and 7 show the device according to a further exemplaryembodiment. The device comprises two parts. In particular, the devicehas a first part 23, which consists of a first housing 11 and a secondhousing 15, and a second part 24, which consists of an energy supply 16.

FIG. 5 shows the first part 23 of the device. The first housing 11comprises the piezoelectric transformer 1. The second housing 15comprises the control circuit 14. The first housing 11 and the secondhousing 15 are not detachably connected to each other. A non-detachableconnection is referred to here as a connection that is not detachablewithout damaging the first and/or the second housing 11, 15. Thereby,the first and the second housing 11, 15 are spatially separated fromeach other. Accordingly, the piezoelectric transformer 1 and the controlcircuit 14 are spatially separated from each other.

The second housing 15 comprises a USB plug 25, which makes it possibleto connect the first part 23 to the second part 24. In particular thecontrol circuit 14 can be connected to the energy supply 16 via the USBplug 25.

FIG. 6 shows the first and the second part 23, 24 of the device, whereinboth parts 23, 24 are not connected to one another. FIG. 7 shows thefirst and the second part 23, 24 of the device, wherein both parts 23,24 are not connected to one another.

The second part 24 consists of the energy supply 16. The energy supply16 has a USB plug receptacle 29, which is designed to be connected tothe USB plug 25 of the first part 23. The second part 24 can beconnected to the first part 23 by a USB plug connection. If the twoparts 23, 24 are connected to each other, the control circuit 14 issupplied with a voltage by the energy supply 16. In alternativeembodiments, the first and the second part 23, 24 can be connected byanother plug connection, for example, a bayonet connection.

The second housing 15 does not comprise a built-in rechargeable battery,charging electronics and a DC/DC converter. Accordingly, the first part23 of the device can be small and compact. The first part 23 of thedevice can be impervious to impact loads.

The first part 23 of the device can be designed to be connected to anyUSB accessory via the USB plug 25. For example, a USB extension cable, aUSB stand, a USB power bank or a USB power supply can be connected tothe first part 23. Furthermore, the control circuit 14 can be connectedto a USB interface of a computer via the USB plug 25. Thereby, aconfiguration of the device can be made via the computer. Alternativelyor in addition to the USB connection described here, other standardizedlow-voltage elements or systems are also conceivable for connecting thefirst part 23 with other accessories, for example, a micro-USB.

The device shown in FIGS. 5 to 7 offers the advantage that the firstpart 23 of the device is easily replaceable. The energy supply 16 can beseparated from the first part 23 of the device and connected to anotherpart, which also has a piezoelectric transformer 1 and a control circuit14 in separate housings 11, 15.

The first part 23, comprising the piezoelectric transformer 1 and thecontrol circuit 14, can be replaced as a module. Here, the first part 23can be replaced by another housing, which also has a piezoelectrictransformer 1 and a control circuit 14. The piezoelectric transformer 1is the component of the device that is subject to the greatest signs ofwear. By replacing the first part 23 as a module, it is possible toreplace the piezoelectric transformer 1 with a new transformer withouthaving to replace the entire device. In particular, the energy supply 16can be reused. By replacing the first part 23 as a module, thereplacement can be carried out in a simple manner and, for example,carried out by an end customer.

The first part 23 can be replaced by a similar part. Alternatively, thefirst part can be replaced by a part in which a nozzle is provided,which is designed to form a plasma beam generated by the device or toform a dielectric barrier.

FIG. 8 shows an alternative embodiment of the first part 23 of thedevice. Here, the first part 23 comprises a first housing 11, in whichthe piezoelectric transformer 1 is arranged, and a second housing 15, inwhich the control circuit 14 is arranged. The second housing 15comprises a USB plug 25. Via the USB plug 25, the second housing 15 canbe connected to the energy supply 16. The first housing 11 and thesecond housing 15 are connected to each other via the cable 17.

FIG. 9 shows a further exemplary embodiment of the device. In FIG. 9,only the first housing 11 is shown, which comprises the piezoelectrictransformer 1. The first housing 11 is designed as a portable handhelddevice.

The first housing 11 also comprises a fan 26, which serves as a processmedium supply. The handheld device also has a suction spout 27, intowhich air is sucked up. The suction spout 27 is arranged near a plasmaoutlet opening of the first housing 11. The inner side of the suctionspout 27 is coated with an ozone-degrading coating 28, for example, madeof manganese dioxide or iron oxide. Irritant gases, which inevitablyarise during the plasma production, are sucked up via the suction spout27, so that the ozone can be broken down quickly and effectively.

The first housing 11 can also comprise a nozzle or a nozzle attachment,which forms the shape of the plasma beam generated by the piezoelectrictransformer 1. The nozzle can, for example, be designed to fan theplasma beam or to focus the plasma beam.

The first housing 11 can be connected to a second housing 15, whichcomprises the control circuit 14. This connection of the two housings11, 14 is detachable.

The first housing 11, with the piezoelectric transformer 1 and thenozzle, can be removed from the device and replaced as a module. Thefirst housing can be replaced by a third housing, which also comprises apiezoelectric transformer 1 and a nozzle. The piezoelectric transformer1 is the component of the device that is subject to the greatest signsof wear. By replacing the first housing as a module, it is possible toreplace the piezoelectric transformer 1 with a new transformer withouthaving to replace other elements arranged in the second housing. Forexample, the control circuit 14 can be reused. By replacing the firsthousing as a module, the replacement can be carried out in a simplemanner and, for example, carried out by an end customer.

FIG. 10 shows the first housing 11 according to a further exemplaryembodiment. The piezoelectric transformer 1 is arranged in the firsthousing 11.

The first housing 11 comprises an opening, which is sealed by a couplingplate 30. The coupling plate 30 comprises a non-conductive material. Thecoupling plate 30 forms a dielectric barrier, wherein plasma can beignited on the outer side of the coupling plate 30.

On the side of the coupling plate 30, which points away from thepiezoelectric transformer 1 there is arranged a metallization 38. Themetallization 38 influences the electric field generated by thepiezoelectric transformer 1. In this way, the shape of a plasma ignitedon the outer side of the coupling plate 30 can be influenced. By acorresponding shaping of the metallization 38, the plasma can be bundledor fanned out.

The device can have a set of coupling plates 30, which are eachconnectable to the first housing 11. The coupling plates 30 differ herein each case in the form of their metallizations 38. For example, thedevice can have a first coupling plate 30, which has a metallization,which leads to a bundling of a plasma beam on the outer side of thefirst coupling plate 30. Furthermore, the device can have a secondcoupling plate 30, which comprises a differently formed metallization,which leads to a fanning of a plasma beam on the outer side of the firstcoupling plate 30. Depending on the application of the device, the firsthousing 11 can be connected either to the first coupling plate 30 or tothe second coupling plate 30. The coupling plates 30 can be replaceable.

In the first housing there are furthermore arranged a fan 31, acatalytic converter 32 and a heat exchanger 33. The first housing 11furthermore comprises a tubular housing element 34, in which thepiezoelectric transformer 1 is arranged. Also, the fan 31 and thecatalytic converter 32 are arranged in the tubular housing element 34.

The fan 32 is designed to cause a circulating air operation within thefirst housing 11. In this case, air or another process medium is guidedalong the piezoelectric transformer 1, then emerges from the tubularhousing element 34 and is retracted again into this at a back of thetubular housing element 34. The flow of the process medium is marked inFIG. 10 by arrows. In the flow direction of the process medium duringcirculating air mode, the catalytic converter 32, the fan 31 and thepiezoelectric transformer 1 are arranged in this order in the tubularhousing element 34. The catalytic converter 32 is arranged in such a waythat the process medium is first guided through the catalytic converter32 before it again reaches the piezoelectric transformer 1.

The catalytic converter 32 is designed to break down an irritant gas, inparticular ozone. For example, the catalytic converter 32 can be anactivated-carbon filter. Alternatively or in addition to theactivated-carbon filter, the catalytic converter can have a filter basedon manganese dioxide or a filter based on MnO₂. Manganese dioxide canherein be present in the form of a coating.

The process medium is ionized on the piezoelectric transformer 1.Thereby ozone and plasma are generated. Plasma is also generated outsidethe first housing 11 by a dielectric barrier discharge via the couplingplate 30. The ozone and other irritant gases remain within the firsthousing 11 and are supplied to the catalytic converter 32 due to thecirculating air operation and broken down there.

When operating the piezoelectric transformer 1, this is heated so thatsignificant heat is emitted from the transformer 1 to the interior ofthe housing 11. Also, during the ionization of the process medium,further heat forms within the first housing 11. To prevent overheatingof the interior of the first housing 11, the first housing 11 comprisesa heat exchanger 35. The heat exchanger 35 is arranged at the end of thefirst housing 11 located opposite from the coupling plate 30. The heatexchanger 35 is designed to release heat located in the first housing 11into an environment.

FIGS. 11 to 13 show an alternative embodiment of the mounting 12 shownin FIG. 3, to which the piezoelectric transformer 1 can be attached. Themounting 12 is composed of two identical half shells 12 a, 12 b that canbe connected to each other.

FIG. 11 shows a first half shell 12 a of the mounting 12. FIG. 12 alsoshows the first half shell 12 a of the mounting 12, wherein thepiezoelectric transformer 1 and two contact elements 19 for itscontacting are furthermore shown. FIG. 13 shows both half shells 12 a,12 b of the mounting 12 as well as the piezoelectric transformer 1attached in the mounting 12 and the contact elements 19 for itscontacting.

In contrast to the mounting 12 shown in FIG. 3, the mounting 12 shown inFIGS. 11 to 13 has only one support element 18 on which thepiezoelectric transformer 1 rests at its state of rest. A state of restis referred to here as a state at which no electrical voltage is appliedto the transformer 1 and in which no external forces act, for example,as a result of an impact on the device. The support element 18 isarranged in the longitudinal direction at a length of a quarter of thetotal length of the transformer 1. The support element 18 runs in awedge-shape manner so that the transformer 1 rests on the supportelement 18 in a line-shaped manner. The contact elements 19 are arrangedand attached to the first support element 18.

The device does not have any support elements 18 which are located inthe output region of the piezoelectric transformer 1.

The device furthermore comprises two projections 36, 37, which arespaced a few micrometers away from the piezoelectric transformer 1 whenthe transformer 1 is at its state of rest. If the transformer 1 is movedas a result of a transverse movement, for example, due to an impact oras a result of a deformation by an applied voltage, it strikes againstone or both of the projections 36, 37, which thus limit the transverseload of the transformer 1 and form a mechanical end-stop againsttransverse movements of the transformer 1. A first projection 36 isarranged in the center of the transformer 1. The second projection 37 isarranged at the input-side end of the transformer 1.

1. A device comprising: a first housing, in which a piezoelectrictransformer is arranged; and a second housing, in which a controlcircuit is arranged, the control circuit configured to apply an inputvoltage to the piezoelectric transformer, wherein the piezoelectrictransformer is configured to ionize a process medium, and wherein thedevice is configured to: provide a circulating air operation so that theprocess medium is guided from the piezoelectric transformer through acatalytic converter and then back to the piezoelectric transformer, andgenerate a non-thermal atmospheric pressure plasma.
 2. The deviceaccording to claim 1, wherein the first housing comprises a coatingconfigured to eradicate irritant gases.
 3. The device according to claim2, wherein the coating comprises manganese dioxide, iron oxide, othermetal oxides, bare metal surfaces or surface coated with metalcatalysts, or lacquers.
 4. The device according to claim 1, furthercomprising at least one control element arranged in the first housing orthe second housing, wherein the control element is configured to controlgeneration of the plasma.
 5. The device according to claim 1, whereinthe control circuit comprises a time circuit configured to: apply theinput voltage to the piezoelectric transformer for a predefined periodof time, and not apply any input voltage to the piezoelectrictransformer at a predefined pause interval between two periods of time,and wherein an application of the input voltage is prevented for aduration of the pause interval.
 6. The device according to claim 1,wherein the piezoelectric transformer is configured to generatepiezoelectrically ignited microplasma on an output-side end face of thepiezoelectric transformer.
 7. The device according to claim 1, whereinthe first housing and the second housing are separate from each other.8. The device according to claim 1, wherein the control circuit and thepiezoelectric transformer are connected to each other via a cable. 9.The device according to claim 8, wherein the cable has a length of atleast 1 cm.
 10. The device according to claim 1, wherein the firsthousing comprises a nozzle arranged in front of an end face of thepiezoelectric transformer, the nozzle being configured to form a plasmabeam generated by the piezoelectric transformer.
 11. The deviceaccording to claim 1, further comprising a third housing, in which asecond piezoelectric transformer is arranged, wherein the first housingis replaceable by the third housing.
 12. The device according to claim1, wherein the first housing is configured to eradicate irritant gasesproduced during plasma production.
 13. The device according to claim 12,wherein the first housing comprises a filter and/or a closed gasguidance system and/or a suction device configured to eradicate theirritant gases.
 14. The device according to claim 1, further comprisinga control mechanism configured to adjust an amount and/or a compositionof the process medium supplied to the piezoelectric transformer.
 15. Thedevice according to claim 1, further comprising an attachment attachedto the first housing, wherein the attachment forms a dielectric barrierimmediately in front of an output-side end face of the piezoelectrictransformer so that the device is configured to ignite the plasma bydielectric barrier discharge on a side of the dielectric barrier facingaway from the piezoelectric transformer.
 16. The device according toclaim 1, wherein a plurality of piezoelectric transformers are arrangedin the first housing.
 17. The device according to claim 1, wherein thefirst housing and the second housing are formed by two chambers of aninjection-molded part.
 18. The device according to claim 1, wherein thefirst housing and the second housing are separated from each other in awatertight manner.
 19. The device according to claim 1, wherein thefirst housing and the second housing are separated from each other in agastight manner.
 20. The device according to claim 1, further comprisingan energy supply arranged in the second housing.
 21. The deviceaccording to claim 1, wherein the device is a portable handheld device.22. The device according to claim 1, wherein a process-gas-supply isarranged in the second housing, and wherein the device comprises a hoseconfigured to guide the process medium from the process-gas-supply outof the second housing to the piezoelectric transformer arranged in thefirst housing.
 23. The device according to claim 1, further comprising asuction spout configured to suck up irritant gas produced by thepiezoelectric transformer, wherein the irritant gas is eradicated in thesuction spout.
 24. The device according to claim 1, further comprising asensor configured to determine a filling level, a temperature or ahumidity inside or in surroundings of an active space.
 25. The deviceaccording to claim 1, further comprising circuit components of a remotecontrol configured to control a control system.
 26. The device accordingto claim 1, further comprising circuit elements configured to reportoperating times, errors, status information, and operating parameters.27. The device according to claim 1, further comprising one or moreindicators configured to optically or acoustically signaling of one ormore operating parameters.
 28. The device according to claim 1, whereinthe device is configured to enable, accelerate or catalyze chemicalreactions.
 29. The device according to claim 1, wherein the device isconfigured to activate or to sterilize surfaces.
 30. The deviceaccording to claim 1, wherein the device is configured to clean or totreat wounds of a human or an animal.
 31. The device according to claim1, further comprising a fan arranged in the first housing, wherein thefan is configured to ensure the circulating air operation therebyguiding the process medium ionized by the piezoelectric transformer inthe first housing within a circuit, and through the catalytic converterbefore the process medium is supplied back to the piezoelectrictransformer.
 32. The device according to claim 1, wherein the firsthousing comprises a heat exchanger configured to dissipate heat from aninside of the first housing to an environment.
 33. The device accordingto claim 1, further comprising at least one first projection, which isspaced apart from the piezoelectric transformer when the piezoelectrictransformer is at a state of rest, and which forms an end-stop againsttransverse movements of the piezoelectric transformer, wherein an inputregion of the piezoelectric transformer rests on a first supportelement.
 34. The device according to claim 33, wherein the firstprojection is arranged at half a length of the piezoelectrictransformer.
 35. The device according to claim 33, further comprising asecond projection, which is spaced apart from the piezoelectrictransformer when the piezoelectric transformer is at the state of rest,and which forms the end-stop against the transverse movements of thepiezoelectric transformer, wherein the second projection is arranged atan input-side end of the piezoelectric transformer.
 36. The deviceaccording to claim 1, wherein the first housing is sealed by a couplingplate, the coupling plate comprising a dielectric material, and whereina metallization is arranged on an outer side of the coupling platepointing away from the piezoelectric transformer.
 37. The deviceaccording to claim 1, wherein the first housing is connectable to afirst coupling plate comprising a first dielectric material and a firstmetallization on an outer side pointing away from the piezoelectrictransformer, or to a second coupling plate comprising a seconddielectric material and a second metallization on an outer side pointingaway from the piezoelectric transformer, and wherein the firstmetallization has a different shape than the second metallization. 38.An active space comprising: the device according to claim 1; and a gasvolume that is airtight or a gas volume that is not airtight.
 39. Theactive space according to claim 38, wherein the active space comprises acover, wherein the device is arranged on the cover, and wherein a plasmaoutlet opening of the device points away from the cover.
 40. The activespace according to claim 39, further comprising a sensor configured todetect an opening and closing of the cover, wherein the device isconfigured to produce the plasma after closing the cover.
 41. A devicecomprising: a first housing, in which a piezoelectric transformer isarranged; and a second housing, in which a control circuit is arranged,the control circuit configured to apply an input voltage to thepiezoelectric transformer, wherein the first housing comprises a coatingconfigured to eradicate irritant gases, and wherein the device isconfigure to produce a non-thermal atmospheric pressure plasma.
 42. Adevice for producing a non-thermal atmospheric pressure plasma, thedevice comprising: a first housing, in which a piezoelectric transformerand at least one control element are arranged; and a second housing, inwhich a control circuit is arranged, the control circuit is configuredto apply an input voltage to the piezoelectric transformer, wherein thecontrol element is configured to control generation of the plasma.
 43. Amethod for producing a non-thermal atmospheric pressure plasma, themethod comprising: providing a device comprising a first housing, inwhich a piezoelectric transformer and a catalytic converter arearranged; operating the device in a circulating air operation, wherein aprocess medium ionized by the piezoelectric transformer in the firsthousing and guided within a circuit, and thereby guided through thecatalytic converter before the process medium is supplied back to thepiezoelectric transformer.